Peritoneal dialysis sensor apparatus systems, devices and methods

ABSTRACT

A sensor apparatus and sensor apparatus system for use in conjunction with a cassette-based peritoneal dialysis system is described, including a disposable cassette. In some embodiments, the cassette includes a thermal well for permitting the sensing of various properties of a dialysate. The thermal well includes a hollow housing of a thermally conductive material. In other embodiments, the cassette includes sensor leads for sensing of various properties of a dialysate. The thermal well has an inner surface shaped so as to form a mating relationship with a sensing probe. The mating thermally couples the inner surface with a sensing probe. In some embodiments, the thermal well is located on a disposable portion and the sensing probe on a reusable portion.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from the following U.S. ProvisionalPatent Applications, all of which are hereby incorporated herein byreference in their entireties:

U.S. Provisional Patent Application No. 60/904,024 entitled HemodialysisSystem and Methods filed on Feb. 27, 2007; and

U.S. Provisional Patent Application No. 60/921,314 entitled SensorApparatus filed on Apr. 2, 2007.

This application is also related to U.S. patent application Ser. No.11/871,821, published as U.S. Patent Application Publication No.2008/0240929 entitled Sensor Apparatus Systems, Devices and Methods,which is hereby incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present invention relates to sensor systems, devices, and methods,and more particularly to peritoneal dialysis systems, devices, andmethods for sensors, sensor apparatus, and sensor apparatus systems.

BACKGROUND ART

Peritoneal Dialysis (PD) periodically infuses sterile aqueous solutioninto the peritoneal cavity. This solution is called peritoneal dialysissolution, or dialysate. Diffusion and osmosis exchanges take placebetween the solution and the bloodstream across the natural bodymembranes. These exchanges remove the waste products that the kidneysnormally excrete. The waste products typically consist of solutes likesodium and chloride ions, and the other compounds normally excretedthrough the kidneys like urea, creatinine, and water.

Automated Peritoneal Dialysis (APD) is a popular form of PD. APD uses amachine, called a cycler, to automatically infuse, dwell, and drainperitoneal dialysis solution, or dialysate, to and from the patient'speritoneal cavity. A typical APD sequence lasts for several hours. Itoften begins with an initial drain cycle to empty the peritoneal cavityof spent dialysate. The APD sequence then proceeds through a successionof fill, dwell, and drain phases that follow one after the other. Eachfill/dwell/drain sequence is called a cycle. During the fill phase, thecycler transfers a predetermined volume of fresh, warmed dialysate intothe peritoneal cavity of the patient. The dialysate remains (or“dwells”) within the peritoneal cavity for a time. This is called thedwell phase. During the drain phase, the cycler removes the spentdialysate from the peritoneal cavity. The number of fill/dwell/draincycles that are required during a given APD session depends upon thetotal volume of dialysate prescribed for the patient's APD regime.

Systems for performing peritoneal dialysis are known in the art. U.S.Pat. No. 5,350,357, entitled Peritoneal Dialysis Systems Employing aLiquid Distribution and Pumping Cassette that Emulates Gravity, andother patents, describe a cassette-based peritoneal dialysis system. PDsystems of the type described in U.S. Pat. No. 5,350,357 have been verywell received by professionals and patients for the treatment ofend-stage renal disease.

Despite the success of such peritoneal dialysis systems, there is a needfor sensor apparatus and sensor apparatus systems capable of sensing thetemperature, the conductivity, and/or other properties of the dialysatepresent in the cassette.

Additionally, there is a need for an accurate measurement apparatus tomeasure the temperature, conductivity, and/or other property of thedialysate in the cassette while avoiding contamination between with themeasurement apparatus and the dialysate. There is also a need for anaccurate measurement apparatus that can measure the temperature,conductivity, and/or other condition of a dialysate where such dialysateis contained in and/or flowing through a disposable cassette such thatpart or all of the sensor apparatus can be reused and need not bedisposed of along with the disposable cassette.

SUMMARY OF THE INVENTION

In accordance with one aspect of the invention there is provided asystem for performing peritoneal dialysis including a sensor apparatussystem for determining one or more properties of dialysate solution in acassette, the system comprising a peritoneal dislysis cycler; a thermalsensor in said cycler having a sensing end and a connector end; a probetip thermally coupled to said sensing end of the thermal sensor andattached to said cycler, the probe tip adapted for thermal coupling withan inner surface of a well installed in the cassette; and at least twoleads connected to said connector end of said thermal sensor, wherebythermal energy is transferred from said well to said thermal sensor andwhereby temperature information is conveyed through said leads. Invarious alternative embodiments, the sensing probe may further include athird lead attached to one of the probe housing, the thermal sensor, andthe probe tip for permitting conductivity sensing. Alternatively, thesensing probe may further include a conductivity sensor attached to oneof the probe housing, the thermal sensor, and the probe tip forpermitting conductivity sensing; and a third lead attached to theconductivity sensor for transmitting conductivity information. Aurethane resin may be included between said probe tip and said probehousing. The probe tip may include a flange for mating with the housing.

In various alternative embodiments of the sensor apparatus systemdescribed above, thermal epoxy may be included between said thermalsensor and said probe tip. The probe tip may be copper, steel, or ametal including at least one of silver, copper, steel, and stainlesssteel. In various embodiments, the housing may be plastic or metal. Thehousing may include a flange disposed about said probe housing, and aspring may be used in conjunction with the flange. The housing mayinclude an integrated flexible member.

Some embodiments of this aspect of the present invention include a wellof a predetermined size and shape. The well mates with the probe and theprobe tip is thermal coupled to said well.

In accordance with one aspect of the present invention the well includesa hollow housing of a thermally conductive material. The housing has anouter surface and an inner surface. The inner surface is a predeterminedshape so as to form a mating relationship with a sensing probe. Themating thermally couples the inner surface with a sensing probe.

Some embodiments of this aspect of the present invention include apredetermined volume of thermal grease on the inner surface of the well.

In accordance with one aspect of the present invention, method fordetermining temperature and/or conductivity of a dialysate in a cassetteis described. The method includes the following steps: installing atleast one well in a cassette; thermally coupling a well and a sensingprobe such that temperature and conductivity can be determined;transferring thermal and conductivity signals through at least 3 leadsfrom the sensing probe; and determining temperature and conductivityusing the signals.

In accordance with another aspect of the invention there is provided acassette for performing peritoneal dialysis, wherein such cassetteincludes a thermal well in a fluid path for at least one of transmittingtemperature and permitting conductivity sensing of fluid passing throughthe conduit, wherein the well is adapted for interconnection with asensor.

In various alternative embodiments, the apparatus may be configured sothat a portion of the well comes into contact with fluid in the conduitor so that no portion of the well comes into contact with fluid in theconduit. The fluid conduit in the cassette may include plastic tubing ormetal tubing.

In various embodiments, the cassette containing the fluid path comprisesa rigid body overlaid on one or more sides with a flexible diaphragm. Invarious embodiments the flexible diaphragm cassette includes one or morepump chambers and/or one or more value stations. In various embodiments,one or more thermal wells are positioned on the edge of the cassette. Incertain of these embodiments, one or more wells are positioned on thebottom edge of the cassette.

The cassette and the well may be integrally formed from the samematerial.

Alternatively, the well may be coupled to the cassette, e.g., using atleast one of press fit connection, flexible tabs, adhesive, ultrasonicweld, and a retaining plate and fastener. An o-ring may be disposedbetween the well and the fluid conduit. The o-ring may include one of around cross-section, a square cross-section, and an X-shapedcross-section. The well may include a groove to receive a portion of theo-ring. A portion of the well in contact with the conduit may beflexible so as to deform the conduit and may include a plurality of cutsto provide such flexibility.

In accordance with another aspect of the invention there is provided afluid pumping cassette comprising at least one pump chamber, one valvestation, and one thermal well for at least one of transmittingtemperature and permitting conductivity sensing of fluid passing throughthe conduit, wherein the well is adapted for interconnection with asensor.

In accordance with another aspect of the invention there is provided asensing system comprising at least one sensing probe and at least onewell installed in a cassette, the well in communication with the sensingprobe for at least one of thermal sensing and conductivity sensing.

These aspects of the invention are not meant to be exclusive orcomprehensive and other features, aspects, and advantages of the presentinvention are possible and will be readily apparent to those of ordinaryskill in the art when read in conjunction with the followingdescription, the appended claims, and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing features of the invention will be more readily understoodby reference to the following detailed description, taken with referenceto the accompanying drawings, wherein:

FIG. 1 is a perspective view an exemplary cassette-based automatedperitoneal dialysis system;

FIG. 2 is a perspective view of the cycler associated with the systemshown in FIG. 1;

FIG. 3 is a perspective view of the cassette and the associateddisposable liquid delivery set associated with the system shown in FIG.1;

FIGS. 4 and 5 are perspective views of loading the disposable cassetteattached to the set shown in FIG. 3 into the cycler for use;

FIG. 6 is an exploded perspective view of one side of the cassetteattached to the disposable set shown in FIG. 3;

FIG. 6A is a plan view of the one side of the cassette shown in FIG. 6,showing the liquid paths within the cassette;

FIG. 6B is a plan view of the other side of the cassette shown in FIG.6, showing the pump chambers and valve stations within the cassette;

FIG. 6C is an enlarged side section view of a typical cassette valvestation shown in FIG. 6B;

FIG. 7A is a section view of the back side of an exemplary cassette;

FIG. 7B is a side view of the side of an exemplary cassette;

FIG. 7C is a section view of the front of an exemplary cassette;

FIG. 8 is a view of an exemplary cassette and thermal wells;

FIG. 9 is a pictorial view of a thermal well according to one embodimentof the sensing apparatus;

FIG. 10 is a cross sectional view of an exemplary embodiment of thethermal well;

FIGS. 11A and 11B show section views of embodiments of thermal wellshaving variable wall thickness;

FIG. 12 is a view of an exemplary cassette with thermal wells installed;

FIG. 13 is a view of the thermal wells extending into a fluid line of anexemplar cassette;

FIG. 14 is a close up certain features of FIG. 13;

FIG. 15 is a section view of one embodiment of a sensing probe coupledto a thermal well installed in a cassette and suspended by a spring;

FIG. 16 is a section view showing an embodiment of the cassette engagedwith a housing and illustrating engagement of sensing probes located inthe housing with sensor ports of the cassette;

FIGS. 16A and 16B are embodiments of the sensing apparatus where thethermal well is a continuous part of the fluid line;

FIGS. 17A and 17B are embodiments of the sensing apparatus where thethermal well is a separate part from the fluid line;

FIGS. 18A and 18B are embodiments of the sensing apparatus showingvarious lengths and widths of the thermal well;

FIGS. 19A-19S are sectional views of various embodiments of the thermalwell embedded in a fluid line;

FIG. 20 is a section side view of one embodiment of the sensing probe;

FIG. 21 is an exploded view of the embodiment shown in FIG. 8;

FIG. 22 is a sectional view of an alternate embodiment of the tip of thesensing probe;

FIG. 23 is an alternate embodiment of the sensing probe;

FIG. 24 is an alternate embodiment of the sensing probe;

FIG. 25 is a side view of an alternate embodiment of the sensing probe;

FIG. 26 is a section view of a sensing probe coupled to a thermal well;

FIG. 27 is an alternate embodiment of the sensing probe;

FIG. 28 is a section view of a sensing probe coupled to a thermal well;

FIG. 29 is an alternate embodiment of the sensing probe shown in FIG.14A;

FIG. 30 is a sectional view of one exemplary embodiment of the sensorapparatus;

FIG. 31 shows an alternate embodiment of a sensing probe coupled to athermal well;

FIG. 32 is a section view of one embodiment of a sensing probe coupledto a thermal well and suspended by a spring;

FIG. 33 is a section view of one embodiment of a sensing probe in ahousing;

FIG. 34 is a section view of one embodiment of a sensing probe in ahousing;

FIG. 35 is a section view of one embodiment of a sensing probe in ahousing; and

FIG. 36 is a section view of a fluid line with a sensor apparatus.

It should be noted that the foregoing figures and the elements depictedtherein are not necessarily drawn to consistent scale or to any scale.Unless the context otherwise suggests, like elements are indicated bylike numerals.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Various aspects of the present invention are described below withreference to various exemplary embodiments. It should be noted thatheadings are included for convenience and do not limit the presentinvention in any way.

1. Pertinoneal Dialysis Utilizing a Cassette-Based System

FIG. 1 shows an exemplary cassette-based automated peritoneal dialysissystem 10. The system 10 includes three principal components. These area set 12 (including a cassette); a cycler 14 (shown in FIGS. 1 and 2)that interacts with the cassette to pump liquid; and a controller 16that governs the interaction to perform a selected APD procedure. In theillustrated and preferred embodiment, the cycler and controller arelocated within a common housing 82.

The cycler 14 is intended to be a durable item capable of long term,maintenance free use. As FIG. 2 shows, the cycler 14 also presents acompact footprint, suited for operation upon a table top or otherrelatively small surface normally found in the home. The cycler 14 isalso lightweight and portable.

The set 12 is intended to be a single use, disposable item. The userloads the set 12 on the cycler 14 before beginning each APD therapysession. The user removes the set 12 from the cycler 14 upon thecompleting the therapy session and discards it.

In use (as FIG. 1 shows), the user connects the set 12 to his/herindwelling peritoneal catheter 18. The user also connects the set 12 toindividual bags 20 containing sterile dialysis solution for infusion.The set 12 also connects to a bag 22 in which the dialysis solution isheated to a desired temperature (typically to about 37 degrees C.)before infusion.

Alternatively, as described in more detail below, the set may beconnected to other sources of dialysate. For example, the set may beconnected to a bag that contains two or more components that areseparately stored from each other, such as in a multi-chamber container,until the components are mixed together to form the dialysate. In otherembodiments, the set may be connected to a system for preparingdialysate. The system may prepare all or substantially all of thedialysate necessary for a complete PD treatment in one batch, mayprepare the dialysate in a number of smaller batches, or may prepare thedialysate in real time or close to real time to its use.

The controller 16 paces the cycler 14 through a prescribed series offill, dwell, drain cycles typical of an APD procedure. During the fillphase, the cycler 14 infuses the heated dialysate through the set 12 andinto the patient's peritoneal cavity. Following the dwell phase, thecycler 14 institutes a drain phase, during which the cycler 14discharges spent dialysis solution from the patient's peritoneal cavitythrough the set into a nearby drain (not shown).

As FIG. 3 best shows, the set 12 includes a cassette 24 to which lengthsof flexible plastic tubes 26/28/30/32/34 are attached.

The cassette 24 serves in association with the cycler 14 and thecontroller 16 to direct liquid flow among the multiple liquid sourcesand destinations that a typical APD procedure requires. As will bedescribed in greater detail later, the cassette 24 provides centralizedvalving and pumping functions in carrying out the selected APD therapy.

FIGS. 6, 6A and 6B show the details of the cassette 24. As FIG. 6 shows,the cassette 24 includes an injection molded body having front and backsides 58 and 60. For the purposes of description, the front side 58 isthe side of the cassette 24 that, when the cassette 24 is mounted in theholder 100, faces away from the user.

A flexible diaphragm 59 and 61 overlies the front side and back sides 58and 60 of the cassette 24, respectively.

The cassette 24 is preferably made of a rigid medical grade plasticmaterial. The diaphragms 59/61 are preferably made of flexible sheets ofmedical grade plastic. The diaphragms 59/61 are sealed about theirperipheries to the peripheral edges of the front and back sides 58/60 ofthe cassette 24.

The cassette 24 forms an array of interior cavities in the shapes ofwells and channels. The interior cavities create multiple pump chambersP1 and P2 (visible from the front side 58 of the cassette 24, as FIG. 6Bshows). The interior cavities also create multiple paths F1 to F9 toconvey liquid (visible from the back side 60 of the cassette 24, asFIGS. 6 and 6A shows). The interior cavities also create multiple valvestations V1 to V10 (visible from the front side 58 of the cassette 24,as FIG. 6B shows). The valve stations V1 to V10 interconnect themultiple liquid paths F1 to F9 with the pump chambers P1 and P2 and witheach other.

The number and arrangement of the pump chambers, liquid paths, and valvestations can vary.

A typical APD therapy session usually requires five liquidsources/destinations. The cassette 24 that embodies the features of theinvention provides these connections with five exterior liquid lines(i.e., the flexible tubes 26 to 32), two pump chambers P1 and P2, nineinterior liquid paths F1 to F9, and ten valve stations V1 to V10.

The two pump chambers P1 and P2 are formed as wells that open on thefront side 58 of the cassette 24. Upstanding edges 62 peripherallysurround the open wells of the pump chambers P1 and P2 on the front side58 of the cassette 24 (see FIG. 6B).

The wells forming the pump chambers P1 and P2 are closed on the backside 60 of the cassette 24 (see FIG. 6), except that each pump chamberP1 and P2 includes a vertically spaced pair of through holes or ports64/66 that extend through to the back side 60 of the cassette 24.

As FIGS. 6, 6A and 6B show, vertically spaced ports 64(1) and 66(1) areassociated with pump chamber P1. Port 64(1) communicates with liquidpath F6, while port 66(1) communicates with liquid path F8.

As FIGS. 6, 6A and 6B also show, vertically spaced ports 64(2) and 66(2)are associated with pump chamber P2. Port 64(2) communicates with liquidpath F7, while port 66(2) communicates with liquid path F9.

As will become apparent, either port 64(1)/(2) or 66(1)/(2) can serveits associated chamber P1/P2 as an inlet or an outlet. Alternatively,liquid can be brought into and discharged out of the chamber P1/P2through the same port associated 64(1)/(2) or 66(1)/(2).

In the illustrated and preferred embodiment, the ports 64/66 are spacedso that, when the cassette 24 is oriented vertically for use, one port64(1)/(2) is located higher than the other port 66(1)/(2) associatedwith that pump chamber P1/P2. As will be described in greater detaillater, this orientation provides an important air removal function.

The ten valve stations V1 to V10 are likewise formed as wells open onthe front side 58 of the cassette 24. FIG. 6C shows a typical valvestation V_(N). As FIG. 6C best shows, upstanding edges 62 peripherallysurround the open wells of the valve stations V1 to V10 on the frontside 58 of the cassette 24.

As FIG. 6C best shows, the valve stations V1 to V10 are closed on theback side 60 of the cassette 24, except that each valve station V_(N)includes a pair of through holes or ports 68 and 68′. One port 68communicates with a selected liquid path F_(N) on the back side 60 ofthe cassette 24. The other port 68′ communicates with another selectedliquid path F_(N), on the back side 60 of the cassette 24.

In each valve station V_(N), a raised valve seat 72 surrounds one of theports 68. As FIG. 6C best shows, the valve seat 72 terminates lower thanthe surrounding peripheral edges 62. The other port 68′ is flush withthe front side 58 of the cassette.

As FIG. 6C continues to show best, the flexible diaphragm 59 overlyingthe front side 58 of the cassette 24 rests against the upstandingperipheral edges 62 surrounding the pump chambers and valve stations.With the application of positive force uniformly against this side 58 ofthe cassette 24 (as shown by the f-arrows in FIG. 6C), the flexiblediaphragm 59 seats against the upstanding edges 62. The positive forceforms peripheral seals about the pump chambers P1 and P2 and valvestations V1 to V10. This, in turn, isolates the pump chambers P1 and P2and valve stations V1 to V10 from each other and the rest of the system.The cycler 14 applies positive force to the front cassette side 58 forthis very purpose.

Further localized application of positive and negative fluid pressuresupon the regions of the diaphragm 59 overlying these peripherally sealedareas serve to flex the diaphragm regions within these peripherallysealed areas.

These localized applications of positive and negative fluid pressures onthe diaphragm regions overlying the pump chambers P1 and P2 serve tomove liquid out of and into the chambers P1 and P2.

Likewise, these localized applications of positive and negative fluidpressure on the diaphragm regions overlying the valve stations V1 to V10will serve to seat and unseat these diaphragm regions against the valveseats 72, thereby closing and opening the associated valve port 68. FIG.6C shows in solid and phantom lines the flexing of the diaphragm 59relative to a valve seat 72.

In operation, the cycler 14 applies localized positive and negativefluid pressures to the diaphragm 59 for opening and closing the valveports.

The liquid paths F1 to F9 are formed as elongated channels that are openon the back side 60 of the cassette 24. Upstanding edges 62 peripherallysurround the open channels on the back side 60 of the cassette 24.

The liquid paths F1 to F9 are closed on the front side 58 of thecassette 24, except where the channels cross over valve station ports68/68′ or pump chamber ports 64(1)/(2) and 66(1)/(2).

The flexible diaphragm 61 overlying the back side 60 of the cassette 24rests against the upstanding peripheral edges 62 surrounding the liquidpaths F1 to F9. With the application of positive force uniformly againstthis side 60 of the cassette 24, the flexible diaphragm 61 seats againstthe upstanding edges 62. This forms peripheral seals along the liquidpaths F1 to F9. In operation, the cycler 14 also applies positive forceto the diaphragm 61 for this very purpose.

As FIGS. 6, 6A and 6B show, five premolded tube connectors27/29/31/33/35 extend out along one side edge of the cassette 24. Whenthe cassette 24 is vertically oriented for use, the tube connectors 27to 35 are vertically stacked one above the other. The first tubeconnector 27 is the uppermost connector, and the fifth tube connector 35is the lowermost connector.

As FIG. 2 shows the cycler 14 carries the operating elements essentialfor an APD procedure within a portable housing 82. The housing 82 alsoincludes an exterior support plate 94 on the top of the cycler housing82 for carrying the heater bag 22 (as FIG. 1 shows). The support plate94 is made of a heat conducting material, like aluminum. ThermocouplesT5/T6 (see FIG. 2) independently monitors the temperature of the heaterbag 22 itself. In one embodiment, the controller 16 includes a heatercontrol algorithm that elevates the temperature of liquid in the heaterbag 22 to about 33 degrees C. before the first fill cycle. A range ofother safe temperature settings could be used, which could be selectedby the user. The heating continues as the first fill cycle proceedsuntil the heater bag temperature reaches 36 degrees C.

2. Alternate Dialysis Systems and Methods

Dialysate solution contained in pre-mixed bags (such as those shown as20 and 22 in FIG. 1) may contain a variety of formulations. Certain ofthese formulations, while perhaps otherwise desirable, may not be stableor may not be as stable as other less desirable solutions. For example,in some formulations, carbon dioxide can pass through the bag materialand the remaining calcium carbonate could then fall out of solution. Ininstances where the dialysate formulation is not stable or less stablethan other solutions, In such instances, when a bag of dialysatesolution may have become unstable, valuable information regardingwhether the formulation of the dialysate solution has change and/orwhether the dialysate solution is safe to use for a PD treatment may bedetermined based on the conductivity of the solution.

Additionally, in other embodiments, the cycler may receive dialysis fromsources other than the pre-mixed bags (shown as 20 and 22 in FIG. 1).For example, the set may be connected to a bag that contains two or morecomponents that are stored separately from each other, such as in amulti-chamber container, until the components are mixed together to formthe dialysate. One embodiment of a multi-chamber container is describedin U.S. Pat. No. 7,122,210, which is hereby incorporated by referenceherein. Such multi-chamber bags allow a variety of different dialysatecompositions to be utilized during PD, including solution containing avariety of buffering agents, including bicarbonate. By way of example,in multi-chamber containers of the type described in U.S. Pat. No.7,122,210, two components are stored in separate, hydraulicallyconnected chambers of a multi-chamber container. The contents of the twochambers are then combined prior to utilization of the dialysatesolution by removing what is called a “peel seal” to hydraulicallyconnect the two chambers and mix the two components. However, due tohuman error or otherwise, the two components may not be properly mixedbefore a patient attempts to use the dialysate to conduct a PDtreatment. In such instances, valuable information regarding whether theformulation of the dialysate solution is appropriate and/or whether thedialysate solution is safe to use for a PD treatment may be determinedbased on the conductivity of the solution.

In other embodiments, the cycler may be connected to a system forpreparing dialysate rather than in bagged dialysate of the typesdescribed above. Such systems may prepare all or substantially all ofthe dialysate necessary for a complete PD treatment in one batch inadvance of the PD treatment, may prepare the dialysate in a number ofsmaller batches before and/or during the PD treatment, or may preparethe dialysate in real time or close to real time during the PDtreatment. Again, in such instances, valuable information regardingwhether the formulation of the dialysate solution is appropriate and/orwhether the dialysate solution is safe to use for a PD treatment may bedetermined based on the conductivity of the solution.

In further embodiments, a heating system other than the support plate 94and associated thermocouples described above may be utilized to maintainthe temperature of the dialysate at a certain temperature or within acertain temperature range. Alternate heating systems include the use ofan in-line heater element. In such instances, determining thetemperature of the dialysate solution and comparing that temperature toa known value, which known value may change from time to time during thePD therapy as discussed above, is valuable.

In each of these instances in which one or more properties of thedialysate is determined, it is also valuable to have both an accuratemeasurement apparatus to measure the temperature, conductivity, and/orother property of the dialysate in the cassette while avoidingcontamination between with the measurement apparatus and the dialysate,such that part or all of the sensor apparatus can be reused and need notbe disposed of along with the disposable cassette.

3. Cassette with Sensor Apparatus for Peritoneal Dialysis

FIGS. 7A-C show another exemplary embodiment of a flexible membranecassette of a similar type to those generally described above. FIGS.7A-C shows back, side, and front views of exemplary cassette 2300. AsFIGS. 7A-C show, the cassette 2300 includes an injection molded bodyhaving back side 2310 shown in FIG. 7A and front side 2311 shown in FIG.7C. A flexible diaphragm (one of which is shown as 59 in FIG. 24)overlies the front side and back side of cassette 2300.

The cassette 2300 is preferably made of a rigid plastic material and thediaphragms are preferably made of flexible sheets of plastic, althoughmany other materials may be utilized.

Exemplary cassette 2300 forms an array of interior cavities in theshapes of wells and channels. In exemplary cassette 2300, the interiorcavities create multiple paths, such as fluid path 2303, to conveyliquid (as FIG. 7A shows). In exemplary cassette 2300, the interiorcavities also create pump chambers, such as pump chambers 2301 and 2302(as FIG. 7C shows) and multiple valve stations, such as valve station2304 (as FIG. 7C shows). In the exemplary cassette 2300, the valvestations, such as valve station 2304, interconnect the multiple liquidpaths, such as fluid path 2303, with pump chambers 2301 and 2302 andwith each other.

In certain embodiments, exemplary cassette 2300 may be utilized inconjunction with a device (not shown here, but of the type generallyshown in FIG. 1, 14) that locally applies positive and negativepressure, including positive and negative fluid pressure of the typedescribed above and in U.S. Pat. No. 5,350,357, on the diaphragm regionsoverlying the valve stations and pump chambers. While many differenttypes of pump chambers and valves may be utilized with cassette of thetypes described herein (or, in certain embodiments, not included atall), exemplary pump chambers and valve stations of the type shown inFIGS. 7A-C are described in more detail above and in U.S. Pat. No.5,350,357, incorporated herein. The presence, number, and arrangement ofthe pump chambers, liquid paths, and valve stations can vary.Additionally, alternative or additional cassette functionality may bepresent in a given cassette.

With further reference to FIGS. 7A-C, exemplary cassette 2300 includessensor ports 2305 and 2306 that extend into fluid path 2303. Sensorports 2305 and 2306 may be used to insert a sensing probe, thermal wellor other sensing element to allow. Exemplary cassette 2300 shows twosensor ports per cassette, but one port, two ports, or more than twoports may be used depending on the configuration of the cassette and thetype of sensor or sensors used.

Again, with reference to FIG. 7A-C, exemplary cassette 2300 is shownwith sensor ports 2305 and 2306 position in the rigid body of cassette2300. In the case of a rigid cassette body with two flexible membranes,one on either side of the rigid body, as shown in FIG. 7A-C, in oneembodiment sensor ports 2305 and 2306 may be position in the rigid bodyportion of the cassette (as shown best in FIG. 7B). However, in otherembodiments, the sensor port may extend though one or more areas of theflexible diaphragm overlying the cassette.

Referring now to FIG. 8, exemplary cassette 2300 is shown with sensorports 2305 and 2306 extending into fluid path 2303 such that a componentplaced in sensor ports 2305 and 2306 would come into direct contact withthe dialysate contained in or flowing through fluid path 2303. FIG. 8additionally shows thermal wells 5100 positioned near sensor ports 2305and 2306. In this embodiment, cassette 2300 and thermal wells 51.00 areseparate parts. In some embodiments, the cassette 2300 and the thermalwell 5100 are made from different materials. For these embodiments, thethermal well 5100 can be made from any materials, including but notlimited to, plastic, metal, ceramic or a combination thereof. Thematerial may depend in some part on the compatibility with the intendeddialysate formulation. In other embodiments, thermal well 5100 could bemade from the same material as cassette 2300. In yet furtherembodiments, thermal well 5100 could be formed as a part of thestructure of the rigid body of cassette 2300.

The length and width of the thermal well 5100 utilized with exemplarycassette 2300 can be any length and width having the desired ortolerable accuracy characteristics and which properly positions anysensor or sensing probe utilized with thermal well 5100 sufficiently incontact with the dialysate contained in or flowing through fluid path2306. The length of thermal well 5100 may impact the fluid flow of thedialysate in fluid path 2303 to a certain extent. It also should beunderstood that the length of the thermal well 5100 may also impact theturbulence of the fluid flow. Thus, the length and width of the thermalwell 5100 may be changed to have greater or lesser impact on the fluidflow and turbulence of the fluid, while mitigating the other variables.

The shape of the thermal well 5100 is also a variable. Any shape desiredis contemplated. However, the shape of the thermal well 5100, as withthe other variables, is determined in part based on the intended use ofthe sensor apparatus. For purposes of description, an exemplaryembodiment is described herein. However, the shape in the exemplaryembodiment is not meant to be limiting. All of the various embodimentsof thermal wells described herein may be used in conjunction withcassettes, such as exemplary cassette 2300.

Referring now FIG. 9 for purposes of description, the thermal well 5100has been divided into three zones. The top zone 5402 communicates withthe sensing probe (not shown); the middle zone 5404 provides the desiredlength of the thermal well 5100. As described above, the length maydictate the level of protrusion into the fluid path. The length isdictated in part by the desired performance characteristics as discussedabove. The middle zone 5404 also isolates the top zone 5402 from theambient. The middle zone 5404 may also serve to locate, fasten or sealthe thermal well 5100 into the cassette.

The bottom zone 5406, which in some embodiments may not be necessary(see FIG. 19K) thus, in these embodiments, the middle zone 5404 and thebottom zone 5406 may be a single zone. However, in the exemplaryembodiment, the bottom zone 5406 is shaped to aid in press fitting thethermal well into an area in the fluid line and may locate and/or fastenthe thermal well 5100 into the fluid line 5108. In other embodiments,zone 5406 may be formed to facilitate various joining methods (see FIGS.19A-19J, 19L-19S)

Referring now to FIG. 10 a cross section of the exemplary embodiment ofthe thermal well 5100 is shown. The dimensions of the exemplaryembodiment of the thermal well 5100 include a length A of approximately0.113 inches (with a range from 0-0.379 inches), a radius B ofapproximately 0.066 inches and a wall thickness C ranging fromapproximately 0.003-0.009 inches. These dimensions are given forpurposes of an exemplary embodiment only. Depending on the variables andthe intended use of the sensing apparatus, the thermal well 5100dimensions may vary, and the various embodiments are not necessarilyproportional.

In some embodiments, the wall thickness can be variable, i.e., the wallthickness varies in different locations of the thermal well. Althoughthese embodiments are shown with variable thicknesses in variouslocations, this is for description purposes only. Various embodiments ofthe thermal well may incorporate varying wall thickness in response tovariables, these varying wall thicknesses can be “mixed and matched”depending on the desired properties of the sensing apparatus. Thus, forexample, in some embodiments, a thinner zone 5404 may be used withthinner zone 5406 and vice-versa. Or, any other combination of “thinner”and “thicker” may be used. Also, the terms used to describe the wallthicknesses are relative. Any thickness desired is contemplated. Thefigures shown are therefore for descriptive purposes and represent twoembodiments where many more are contemplated.

Referring now to FIGS. 11A and 11B, zone 5402 can be thicker or thinneras desired. The thinner zone 5402, amongst other variables, generallyprovides for a faster sensing time while a thicker zone may be usefulfor harsh environments or where sensor damping is desired. Zone 5404 maybe thicker, amongst other variables, for greater strength or thinnerfor, amongst other variables, greater isolation from ambient. Zone 5406can be thinner or thicker depending on the fastening method used.

FIG. 12 shows thermal wells 5100 installed in exemplary cassette 2300.Thermal well 5100 may be installed in exemplary cassette 2300 by use ofthe ways described herein, including adhesive, welding (ultrasonic andotherwise), o-ring, retaining plate, and otherwise. The thermal well5100 used in connection with a cassette may be of various shapes andconfigurations. However, referring now to FIG. 9 for purposes ofdescription, the embodiment of a thermal well 5100 shown may be utilizedin conjunction with a cassette. In the exemplary embodiment shown inFIG. 9, the bottom zone 5406 is shaped to aid in press fitting thethermal well into the sensor port 2305 shown in FIGS. 7A-C and 8.

FIG. 13 further shows thermal well 5100 installed in sensor port 2305and 2306. As may be best shown by FIG. 14, thermal well 5100 extendsinto fluid path 2303 so that thermal well 5100 may come into directcontact with any dialysate contained in or flowing through exemplarycassette 2300.

In certain embodiments of sensor apparatus and sensor apparatus systemsused in conjunction with a flexible membrane cassette, a sensing probemay be installed directly into sensing ports 2305 and 2306 (sensingports 2305 and 2306 as shown in FIGS. 7A-C and 24). In furtherembodiments of sensor apparatus and sensor apparatus systems used inconjunction with a flexible membrane, a sensing probe may be used with athermal well.

As can be seen in FIG. 14, dialysate is in contact with the outside ofzone 5402 of the thermal well 5100. Thermal energy is transferred fromthe dialysate to the thermal well 5100. As may be seen with reference toFIG. 13A-B, the thermal energy can them be further transferred to thetip 6002 of the sensing probe 6000. Thermal energy is then conducted tothe thermal sensor 6014. The thermal sensor 6014 communicates via leads6016 with equipment that can determine the temperature of the dialysatebased on feedback of the thermal sensor 6014. In embodiments whereconductivity sensing is also desired, lead 6018 communicates withequipment that can determine the conductivity of the dialysate. Withrespect to determining the conductivity of the dialysate, in addition tothe lead 6018, a second electrical lead/contact (not shown) would alsobe used. The second lead could be any probe or apparatus capable ofsensing capacitance of the dialysate, including, an electrical contact.

Heat transfer from the tip 6002 to the thermal sensor 6014 may beimproved by the use of a thermal epoxy or thermal grease 6022.

Many different embodiments of sensing apparatus may be used inconnection with a thermal well installed in a flexible cassette,including embodiments similar to those described below. While severalgeometries have been described, many others could be shown to achievedesired performance characteristics.

In certain embodiments, exemplary cassette 2300 may be utilized inconjunction with a device (an exemplary cycler is shown in FIG. 1, 14)that locally applies positive and negative pressure, including positiveand negative fluid pressure of the type described above and in U.S. Pat.No. 5,350,357, on the diaphragm regions overlying the valve stations andpump chambers. When cassette 2300 is utilized in conjunction with apressure applying device (not shown), cassette 2300 may be connected tothe device in a number of different ways and in a number of differentpositions.

Preferably, in certain embodiments, cassette 2300 may be loaded in adevice in other than a horizontal orientation, such as a vertical orsubstantially vertical orientation. Placement of the cassette in avertical or substantially vertical orientation may offer certainadvantages depending on the configuration of the cassette such as toavoid air entrapment and to optimize application of positive andnegative pressure, including positive and negative fluid pressure of thetypes described above and in U.S. Pat. No. 5,350,357, to the cassette.In certain embodiments, non-pneumatic pressure may be applied to thecassette to cause pumping, valving, and/or other functions.

Referring now to FIG. 16, a sensor apparatus system of the typegenerally shown may be used in connection with exemplary cassette 2300.In the system, the sensor apparatus is installed in sensor ports 2305and 2306 (not shown) extending into fluid path 2303. The sensorapparatus includes the sensing probe 6000 and the thermal well 5100. Inthis embodiment, the thermal well 5100 and fluid line 2303 is containedin an exemplary cassette 2300. In certain embodiments, exemplarycassette 2300 is intended to be disposable. Sensing probe 6000 ismounted in a reusable portion. Also in the reusable portion is a spring2801. The spring 2801 and sensing probe 6000 are located in a housing2800. The housing 2800 can be in any machine, container, device orotherwise. In certain embodiments the reusable portion in contained inor otherwise a part of a pressure applying device (such as shown in FIG.1, 14). The spring 2801 can be a conical, a coil spring, wave spring, orurethane spring. Alternatively, any other apparatus for biasing thesensing probe to ensure an appropriate fit in thermal well 5100 may beused, including the apparatus described below.

In certain embodiments, the thermal well 5100 and the sensing probe 6000may include alignment features (of the type shown in FIG. 32, 6702,6704) that aid in the thermal well 5100 and sensing probe 6000 beingaligned. The correct orientation of the thermal well 5100 and thesensing probe 6000 may aid in the mating of the thermal well 5100 andthe sensing probe 6000 to occur. Referring again to FIG. 216, theconfiguration of the housing 2800 may provide the sensing probe 6000with space for lateral movement. This allows the sensing probe 6000 to,if necessary; move laterally in order to align with the thermal well5100 for mating.

In various embodiments, the sensing probe 6000 is configured withrespect to the housing 2800 (as shown in FIG. 16) to facilitateengagement between the sensing probe 6000 and the thermal well 5100 andto aid in establishing full contact of the sensing probe 6000 and thethermal well 5100. Variations of the configurations generally shown inFIGS. 33-35 and described above may be used in conjunction withexemplary cassette 2300.

In other embodiments, the sensing probe may be aligned and positioned byother housing configurations. Thus, the embodiments of the housing shownherein are only some embodiments of housings in which the sensorapparatus can be used. The sensor apparatus generally depends on beinglocated amply with respect to the dialysate. The configurations thataccomplish this can vary depending on the dialysate and the intended useof the sensing apparatus. Further, in some embodiments where the thermalwell is not used, but rather, the sensing probe is used only. Thehousing configurations may vary as well.

In embodiments in which cassette 2300 is loaded into a device, such as apressure applying device or a cycler (as shown in FIG. 1, 14),particularly when cassette 2300 is loaded into the device or cycler in avertical or substantially vertical orientation, it may be preferable forsensor ports 2305 and 2306 to be positioned in the bottom edge ofcassette 2300 (the bottom edge as the cassette is shown in FIG. 7A).Positioning of the sensor ports 2305 and 2306 along the bottom edge ofexemplary cassette 2300 (such that sensor ports 2305 and 2306 andinstalled thermal wells 5100 extend into the bottom fluid line 2303 ofthe cassette) may facilitate engagement with the sensor apparatus asshown in FIG. 28. In certain of these embodiments, the exemplarycassette 2300 with installed thermal wells 51.00 may be placed inposition over sensor probes 6000, and then rotated vertically down andonto the sensor probes 6000.

The sensing apparatus, in some embodiments, is used to senseconductivity of the dialysate within a fluid line within a cassette. Insome embodiments, this is in addition to temperature sensing. In thoseembodiments where both temperature and conductivity sensing is desired,the sensing probe typically includes at least three leads, where two ofthese leads may be used for temperature sensing and the third used forconductivity sensing.

Referring now to FIG. 15, for conductivity sensing, at least two sensors7102, 7104 are located in an area containing the dialysate. In theembodiment shown, the area containing the dialysate is a fluid path 5104inside a fluid line 5108. The conductivity sensors 7102, 7104 can be oneof the various embodiments of sensing probes as described above, or oneof the embodiments of the sensor apparatus embodiments (including thethermal well) as described above.

Referring now to FIG. 16, sensing probes 6000 installed in thermal wells5100 in sensor ports 2305 and 2306 can be used for sensing theconductivity of the dialysate located between sensor ports 2305 and 2306in fluid line 2303. However, in other embodiments, only one of thesensors is one of the embodiments of the sensor apparatus or one of theembodiments of the sensing probe, and the second sensor is anyelectrical sensor known in the art. Thus, in the systems describedherein, conductivity and temperature can be sensed through using eitherone of the sensor apparatus or one of the sensor probes as describedherein and a second capacitance sensor, or one of the sensor apparatusor one of the sensor probes as described herein and an electricalsensor.

Temperature sensing may be used as a part of various safety apparatusand procedures. Temperature sensing may be used to measure thetemperature of the dialysate in the cassette before the dialysate entersthe patient's peritoneum. Alternatively, temperature sensing may be usedto measure the temperature of the dialysate in the cassette before thedialysate enters the patient's peritoneum. In other embodiments,temperature sensing may be used to measure the temperature of thedialysate in the cassette before and after the dialysate enters thepatient's peritoneum. Temperature measurements may be sent to cycler(shown in FIG. 1, 14) and/or the controller (shown in FIG. 1, 16).Temperature measurements may be taken at predetermined times, regular,intervals, or on demand. Temperature measurements may be displayed tothe patient. In other embodiments, the temperature measurements arecompared against a desired value or against a desired range. In certainembodiments, the cycler (shown in FIG. 1, 14) and/or the controller(shown in FIG. 1, 16) may cause a notice or alarm to be displayed to thepatient indicating that the temperature is outside of certainparameters. In other embodiments, the cycler (shown in FIG. 1, 14)and/or the controller (shown in FIG. 1, 16) may not start a PD treatmentif the temperature is outside of certain parameters. In otherembodiments, the cycler (shown in FIG. 1, 14) and/or the controller(shown in FIG. 1, 16) may stop or delay a PD treatment if thetemperature is outside of certain parameters. In various embodiments,the temperature of the dialysate may be measured in one fluid path inthe cassette. In other embodiments, the temperature of the dialysate maybe measured in multiple fluid paths in the cassette or in all fluidpaths in the cassette.

Conductivity sensing may be used (alone or preferably in conjunctionwith temperature sensing) as a part of various safety apparatus andprocedures. Conductivity sensing may be used to measure the conductivityof the dialysate in the cassette before the dialysate enters thepatient's peritoneum to determine if the dialysate solution has theexpected conductivity and thus may be used to determine if the dialysateis of the expected formulation. Conductivity sensing may be used (aloneor preferably in conjunction with temperature sensing) to determine ifthe dialysate in the pre-mixed bag remains stable. In other embodiments,conductivity sensing may be used (alone or preferably in conjunctionwith temperature sensing) to determine if the patient or caregiver hasappropriately removed the seal and mixed the multiple components in amulti-chamber bag. In other embodiments, conductivity sensing may beused (alone or preferably in conjunction with temperature sensing) todetermine if the dialysate prepared in a dialysate preparation system isof the expected conductivity and thus is of the expected formulation,pH, and the like.

In certain embodiments, the cycler (shown in FIG. 1, 14) and/or thecontroller (shown in FIG. 1, 16) may cause a notice or alarm to bedisplayed to the patient indicating that the conductivity of thedialysate (or indicating that the dialysate may not be safe for PDtreatment based on the conductivity of the dialysate) is outside ofcertain parameters. In other embodiments, the cycler (shown in FIG. 1,14) and/or the controller (shown in FIG. 1, 16) may not start a PDtreatment if the conductivity of the dialysate is outside of certainparameters. In other embodiments, the cycler (shown in FIG. 1, 14)and/or the controller (shown in FIG. 1, 16) may stop or delay a PDtreatment if the conductivity of the dialysate is outside of certainparameters. In various embodiments, the conductivity of the dialysatemay be measured in one fluid path in the cassette. In other embodiments,the conductivity of the dialysate may be measured in multiple fluidpaths in the cassette or in all fluid paths in the cassette.

4. Alternate Thermal Well Embodiments

Alternate embodiments of thermal wells are described, often in relationto a fluid line. In most embodiments, the fluid line could be the fluidpath of a cassette, such as fluid path 2303 of exemplary cassette 2300,described above. Alternatively, the principles described below couldalso be applicable to any of the cassette embodiment described herein.

In one exemplary embodiment, a thermal well is used to accommodate asensor probe, such as a temperature sensing probe. The thermal wellcomes into direct contact with a dialysate and the sensing probe doesnot. Based on heat transfer dictated in large part by the thermodynamicproperties of the thermal well and sensing probe construction, thesensing probe can determine the properties of the dialysate withoutcoming into direct contact with the dialysate. The accuracy andefficiency of the sensor apparatus arrangement depends on many factorsincluding, but not limited to: construction, material and geometry ofboth the probe and the thermal well.

Referring now to FIGS. 16A and 16B, two embodiments of the sensorapparatus which includes the thermal well 5100 and the sensing probe5102, are shown in relation to a fluid line 5108. In these embodiments,the thermal well 5100 is integrated into the fluid line 5108. However,in other embodiment, some described below, the thermal well 5100 is notcompletely integrated into the fluid line 5108, i.e., the thermal well5100 can be made from different materials as compared with the fluidline 5108. In alternate embodiments, the thermal well 5100 is notintegrated into any fluid line but can be integrated into anything ornothing at all. For example, in some embodiments, the thermal well 5100can be integrated into a container, chamber, machine, protective sleeve,fluid pump, pump cassette, disposable unit, manifold, or other assembly,sub-assembly, or component. For purposes of the description, anexemplary embodiment is described for illustrative purposes. Theexemplary embodiment includes the embodiment where the thermal well 5100is in a fluid line. However, the sensor apparatus and the thermal wellcan be used outside of a fluid line.

Referring now to FIG. 16A, a side view showing a thermal well 5100formed in a fluid line 5108 which provides the space 5104 for dialysateto flow through, and a sensing probe 5102 is shown. Data from thesensing probe is transmitted using at least one lead 5106. An end viewof FIG. 16A is shown in FIG. 16B.

In this embodiment, the thermal well 5100 is one piece with the fluidline 5108. The total area of the thermal well 5100 can vary. By varyingthe geometry of the thermal well 5100, the variables, including, but notlimited to, the thermal conductivity characteristic of the thermal well5100 and thus, the heat transfer between the thermal well 5100 and thesensing probe 5102 will vary. As described in more detail below, thematerial construction of the thermal well 5100 is another variable inthe sensor apparatus.

In some embodiments, the fluid line 5108 is made from a material havinga desired thermal conductivity. This material may vary depending on thepurpose. The material can be anything including, but not limited to, anyplastic, ceramic, metals or alloys of metals or combinations thereof.

Referring now to FIGS. 17A and 17B, in these embodiments, the fluid line5108 and the thermal well 5100 are separate parts. In some embodiments,the fluid line 5108 and the thermal well 5100 are made from differentmaterials.

FIGS. 16A-16B and FIGS. 17A-17B show relatively simple embodiments ofthe sensor apparatus. Thus, for these embodiments, the sensing apparatusincludes a thermal well 5100 and a sensing probe 5102 where the thermalwell either is integrated as one continuous part with the fluid line5108 or is a separate part from the fluid line 5108. However, manyembodiments of the sensor apparatus are contemplated. Much of thevarious embodiments include variations on the materials and thegeometries of the thermal well 5100 and/or the sensing probe 5102. Thesevariations are dictated by multiple variables related to the intendeduse for the sensor apparatus. Thus, the dialysate and the constraints ofthe desired sensor, for example, the accuracy, time for results and thefluid flow and dialysate characteristics are but a sampling of thevarious constraints that dictate the embodiment used. In most instances,each of the variables will affect at least one part of the embodiment ofthe sensor apparatus.

Thus, multiple variables affect the various embodiments of the sensorapparatus, these variables include but are not limited to: 1) geometryof the thermal well; 2) material composition of the thermal well; 3)material composition of the sensing probe; 4) desired flow rate of thedialysate; 5) length and width of the thermal well; 6) desired accuracyof the sensing probe; 7) wall thicknesses; 8) length and width of thesensing probe; 9) cost of manufacture; 10) dialysate composition andcharacteristics including tolerance for turbulence; 11) geometry ofsensing probe; and 12) desired speed of readings.

In the foregoing, various embodiments of the sensor apparatus aredescribed. The description is intended to provide information on theaffect the variables have on the sensor apparatus embodiment design.However, these are but exemplary embodiments. Many additionalembodiments are contemplated and can be easily designed based on theintended use of the sensor apparatus. Thus, by changing one or more ofthe above mentioned partial list of variables, the embodiment of thesensor apparatus may vary.

Referring now to FIGS. 18A and 18B, two embodiments of the thermal well5100 are shown as different parts from the fluid line 5108. Theseembodiments show two geometries of the thermal well 5100. In FIG. 18A,the geometry includes a longer thermal well 5100. In FIG. 18B, thethermal well 5100 geometry is shorter. The length and width of thethermal well 5100 produce varying properties and accuracies of thethermal conductivity between the thermal well 5100 and the sensing probe5102. Depending on the use of the sensor apparatus, the thermal well5100 geometry is one variable.

Referring now to FIG. 18A the longer thermal well 5100 generallyprovides a greater isolation between the dialysate temperature in thefluid line 5104 and the ambient temperature. Although the longer thermalwell 5100 geometry shown in FIG. 18A may be more accurate, theembodiment shown in FIG. 18B may be accurate enough for the purpose athand. Thus, the length and width of the thermal well 5100 can be anylength and width having the desired or tolerable accuracycharacteristics. It should be understood that two extremes of length areshown in these embodiments; however, any length is contemplated. Thedescription herein is meant to explain some of the effects of thevariables.

Still referring to FIGS. 18A and 18B, the longer thermal well 5100 shownin FIG. 3A may impact the fluid flow of the dialysate in the fluid line5108 to a greater degree than the embodiment shown in FIG. 18B. Itshould be understood that the length of the thermal well 5100 may alsoimpact the turbulence of the fluid flow. Thus, the length and width ofthe thermal well 5100 may be changed to have greater or lesser impact onthe fluid flow and turbulence of the fluid, while mitigating the othervariables.

The shape of the thermal well 5100 is also a variable. Any shape desiredis contemplated. However, the shape of the thermal well 5100, as withthe other variables, is determined in part based on the intended use ofthe sensor apparatus. For purposes of description, an exemplaryembodiment is described herein. However, the shape in the exemplaryembodiment is not meant to be limiting.

The thermal well 5100, in practice, can be embedded into a fluid line5108, as a separate part from the fluid line 5108. This is shown anddescribed above with respect to FIGS. 17A-17B. Various embodiments maybe used for embedding the thermal well 5100 into the fluid line 5108.Although the preferred embodiments are described here, any method orprocess for embedding a thermal well 5100 into a fluid line 5108 can beused. Referring now to FIGS. 19A-19S, various configurations forembedding the thermal well 5100 into the fluid line 5108 are shown. Forthese embodiments, the thermal well 5100 can be made from any materials,including but not limited to, plastic, metal, ceramic or a combinationthereof. The material may depend in some part on the compatibility withthe intended dialysate. The fluid line 5108, in these embodiments, maybe made from plastic, metal, or any other material that is compatiblewith the dialysate.

Referring first to FIG. 19A, the thermal well 5100 is shown press fitinto the fluid line 5108 using the zone 5404 (shown in FIG. 9). In FIG.19B, the thermal well 5100 is shown press fit into the fluid line 5108using the zone 5406. Referring now to FIG. 19C, the thermal well 5100 isshown retained in the fluid line 5108 with flexible tabs 5704, an O-ringis also provided. Referring now to FIG. 19D, the thermal well 5100 isshown inserted into the fluid line 5108 with an O-ring 5702. The thermalwell 5100 is also shown as an alternate embodiment, where the thermalwell 5100 zone 5406 includes an O-ring groove. The O-ring groove can becut, formed, spun, cast or injection molded into the thermal well, orformed into the thermal well 5100 by any other method. FIG. 19E shows asimilar embodiment to that shown in FIG. 19D, however, the O-ring grooveis formed in zone 5406 rather than cut, molded or cast as shown in FIG.19D.

Referring now to FIG. 19F, the thermal well 5100 is shown press fit intothe fluid line 5108, zone 5406 includes flexibility allowing the edge ofzone 5406 to deform the material of the fluid line 5108. Referring nowto FIG. 19G, the thermal well 5100 includes cuts 5706 on the zone 5406providing flexibility of the zone 5406 for assembly with the fluid line5108. An O-ring 5702 is also provided. Although two cuts are shown, agreater number or fewer cuts are used in alternate embodiments.

Referring now to FIG. 19H, the embodiment shown in FIG. 19F is shownwith the addition of an O-ring 5702. Referring to FIG. 19I, the thermalwell 5100 is shown insert molded in the fluid line 5108. Zone 5406 isformed to facilitate or enable assembly by insert molding.

FIG. 19J shows an embodiment where the thermal well 5100 is heat staked5708 to retain the thermal well 5100 in the fluid line 5108. In someembodiments of FIG. 19J, an O-ring 5710 is also included. In thisembodiment, the O-ring 5710 has a rectangular cross section. However, inalternate embodiments, the O-ring may have a round or X-shaped crosssection. Likewise, in the various embodiments described herein having anO-ring, the O-ring in those embodiments can have a round, rectangular orX-shaped cross section, or any cross sectional shape desired.

Referring now to FIG. 19K, the thermal well 5100 is retained in thefluid line 5108 by adhesive 5712. The adhesive can be any adhesive, butin one embodiment, the adhesive is a UV curing adhesive. In alternateembodiments, the adhesive may be any adhesive that is compatible withthe dialysate. In this embodiment, the thermal well 5100 is shownwithout a zone 5406.

Referring now to FIG. 19L, thermal well 5100 is shown ultrasonicallywelded in the fluid line 5108. The zone 5406 is fabricated to enablejoining by ultrasonic welding.

Referring now to FIG. 19M, a thermal well 5100 is shown insert molded inthe fluid line 5108. Zone 5406 is a flange for the plastic in the fluidline 5108 to flow around. In the embodiment shown, the flange is flat,however, in other embodiments; the flange may be bell shaped orotherwise.

Referring now to FIG. 19N, the thermal well 5100 is shown retained inthe fluid line 5108 by a retaining plate 5714 and a fastener 5716.O-ring 5702 is also shown.

Referring now to FIGS. 19O-19P, an end view is shown of a thermal well5100 that is retained in a fluid line 5108 by a retaining ring 5718(FIG. 19O) or in an alternate embodiment, a clip 5720 (FIG. 19P). O-ring5702 is also shown.

Referring now to FIG. 19Q, the embodiment of FIG. 19C is shown with analternate embodiment of the thermal well 5100. In this embodiment of thethermal well 5100 the referred to as zone 5404 in FIG. 4 includes ataper that may allow for easier alignment with a sensing probe, betterisolation of zone 5402 from the ambient and better flow characteristicsin the fluid path. The thermal well 5100 is shown retained in the fluidline 5108 using flexible tabs 5704. An O-ring is also provided.

FIG. 19R shows the embodiment of FIG. 19J with an alternate embodimentof the thermal well 5100. The thermal well 5100 shown in this embodimenthas a taper in zone 5404 that may allow for easier alignment with asensing probe, may allow better isolation of zone 5402 from the ambientand may allow better flow characteristics in the fluid path. Zone 5402provides a hemispherical contact for effective thermal coupling with athermal probe. The thermal well 5100 is heat staked 5708 to retain thethermal well 5100 in the fluid line 5108. In some embodiments of FIG.19R, an O-ring 5710 is also included. In this embodiment, the O-ring5710 has a rectangular cross section. However, in alternate embodiments,the O-ring can have a round or X-shaped cross section.

Referring now to FIG. 19S, the embodiment of FIG. 19H is shown with analternate embodiment of the thermal well 5100. FIG. 19S is shown withthe addition of an O-ring 5702. In this embodiment of the thermal well5100 zone 5404 (as shown in FIG. 4) has convolutions that may allowbetter isolation of zone 5402 from the ambient. While several geometrieshave been shown for zone 5404, many others could be shown to achievedesired performance characteristics.

5. Sensing Probe Embodiments

Various embodiments of systems, devices, and methods for sensorinterface, including direct sensor contact, sensor interface through theuse of a thermal well, or otherwise with various disposable and reusablecomponents are described. Such systems, devices, and methods for sensorinterface can be used with a wide variety of sensors and in a widevariety of applications. Such systems, devices, and methods for sensorinterface are by no means limited to use with the various sensorembodiments or for use in any particular context.

Referring now to FIG. 20, a sectional view of an exemplary embodiment ofa sensing probe 5800 is shown. The housing 5804 is a hollow structurethat attaches to the tip 5802. The tip is made of a highly thermallyconductive material. The housing 5804, in the exemplary embodiment, ismade from a thermally insulative material. In some embodiments, thehousing is made of a thermally and electrically insulative material. Inthe exemplary embodiment, the housing 5804 is made of plastic which is athermally insulative and electrically insulative material. The tip 5802either contacts the dialysate directly, or else is mated with a thermalwell.

In the exemplary embodiment, the tip 5802 is attached to the housing5804 using a urethane resin or another thermal insulator in between(area 5807) the tip 5802 and the housing 5804. Urethane resinadditionally adds structural support. In alternate embodiments, otherfabrication and joining methods can be used to join the tip 5802 to thehousing 5804.

The tip 5802 of the sensing probe 5800 is made of a thermally conductivematerial. The better thermally conductive materials, for example,copper, silver and steel, can be used, however, depending on the desireduse for the sensing probe and the dialysate; the materials may beselected to be durable and compatible for the intended use.Additionally, factors such as cost and ease of manufacture may dictate adifferent material selection. In one exemplary embodiment, the tip 5802is made from copper. In other embodiments, the material can be an alloyof copper or silver, or either solid or an alloy of any thermallyconductive material or element, including but not limited to metals andceramics. However, in the exemplary embodiments, the tip 5802 is madefrom metal.

In the exemplary embodiment, the tip 5802 is shaped to couple thermallywith a thermal well as described in the exemplary embodiment of thethermal well above. In the exemplary embodiment as well as in otherembodiments, the tip 5802 may be shaped to insulate the thermal sensor5808 from the ambient. In the exemplary embodiment, the tip 5802 is madefrom metal.

In alternate embodiments a non-electrically conductive material is usedfor the tip. These embodiments may be preferred for use where it isnecessary to electrically insulate the thermal well from the probe. Inanother alternate embodiment, the tip 5802 may be made from anythermally conductive ceramic.

In the exemplary embodiment, the thermal sensor 5808 is located in thehousing and is attached to the interior of the tip 5802 with a thermallyconductive epoxy 5812. In the exemplary embodiment, the epoxy used isTHERMALBOND, however, in other embodiments; any thermal grade epoxy canbe used. However, in alternate embodiments, thermal grease may be used.In alternate embodiments, an epoxy or grease is not used.

The thermal sensor 5808, in the exemplary embodiment, is a thermistor.The thermistor generally is a highly accurate embodiment. However inalternate embodiments, the thermal sensor 5808 can be a thermocouple orany other temperature sensing device. The choice of thermal sensor 5808may again relate to the intended use of the sensing apparatus.

Leads 5814 from the thermal sensor 5808 exit the back of the housing5804. These leads 5814 attach to other equipment used for calculations.In the exemplary embodiment, a third lead 5816 from the tip 5802 is alsoincluded. This third lead 5816 is attached to the tip on a tab 5818. Thethird lead 5816 is attached to the tip 5802 because in this embodiment,the tip 5802 is metal and the housing is plastic. In alternateembodiments, the housing 5804 is metal, thus the third lead 5816 may beattached to the housing 5804. Thus, the tip 5802, in the exemplaryembodiment, includes a tab 5818 for attachment to a lead. However, inalternate embodiments, and perhaps depending on the intended use of thesensing apparatus, the third lead 5816 may not be included. Also, inalternate embodiments where a third lead is not desired, the tip 5802may not include the tab 5818. Referring now to FIG. 21, an exploded viewof the sensing probe 5800 is shown.

Referring now to FIG. 22 an alternate embodiment of the exemplaryembodiment is shown. In this embodiment, the tip 6002 of the sensingprobe is shown. The tip 6002 includes a zone 6004 that will contacteither a dialysate to be tested or a thermal well. A zone 6006 attachesto the sensor probe housing (not shown). An interior area 6008accommodates the thermal sensor (not shown). In this embodiment, the tip6002 is made from stainless steel. However, in other embodiments, thetip 6002 can be made from any thermally conductive material, includingbut not limited to: metals (including copper, silver, steel andstainless steel), ceramics or plastics.

In the exemplary embodiment, zone 6006 includes a tab 6010. A third lead(as described with respect to FIG. 20, 5816) attaches from the tab 6010.Referring next to FIGS. 23 and 24, the sensing probe 6000 is shownincluding the tip 6002 and the housing 6012. In one embodiment, thehousing 6012 is made from any thermally insulative material, includingbut not limited to, plastic. In one embodiment the housing 6012 is pressfit to the tip 6002, glued or attached by any other method. In oneembodiment, the thermal sensor 6014 is thermally coupled to the tip 6002with thermal grade epoxy or, in alternate embodiments, thermal grease6022. Two leads 6016 from the thermal sensor 6014 extend to the distalend of the housing. In some embodiments, a third lead 6018 is attachedto the tip 6002 from the tab 6010. As discussed above, in someembodiments where the third lead is not desired, the tip 6002 does notinclude a tab 6010.

Referring now to FIG. 24, an alternate embodiment of the sensing probe6000 is shown. In this embodiment, the housing 6012 is a plastic moldedover zone 6006 of the tip 6002 and the leads 6016, and in someembodiments, a third lead 6018.

Referring now to FIG. 25, a full side view of one embodiment of thesensing probe 6000. The sensing probe 6000 includes a housing 6012, atip 6002 and the leads 6016, 6018. Flange 6020 is shown. In someembodiment, flange 6020 is used to mount and/or attachment to equipment.

Referring now to FIG. 26, the sensing probe 6000 is shown coupled to athermal well 5100 which is fastened into a fluid line 5108. In theembodiment as shown, two leads 6016 are shown at the distal end of thesensing probe 6000. And, in some embodiments, a third lead 6018 is alsoincorporated into the sensing probe 6000. FIG. 27 shows an alternateembodiment where the sensing probe 6000 includes two leads 6016 but doesnot include the third lead 6018.

Referring flow to both FIGS. 26 and 27, the tip 6002 of the sensingprobe 6000 is in direct contact with the thermal well 5100 whichincludes a zone 5402. The thermal well 5100 is hollow, and the innerpart of zone 5402 is formed such that it will be in mating contact withthe sensing probe tip 6002. As shown in this embodiment, the thermalwell 5100 is designed to have a mating geometry with the sensing probe6000. Thus, the geometry of the thermal well 5100 may depend on thegeometry of the tip 6002 of the sensing probe 6000 and vice-versa. Insome embodiments, it may be desirable that the sensing probe 6000 doesnot have a tight fit or a perfect mate with the thermal well 5100.

Referring now to FIG. 28, one embodiment of the sensing probe 5800 isshown coupled to a thermal well 5100 which is fastened into a fluid line5108. In the embodiment as shown, two leads 5814 are shown at the distalend of the sensing probe 5800. In some embodiments, a third lead 5816 isalso incorporated into the sensing probe 5800. FIG. 29 shows analternate embodiment where the sensing probe 5800 includes two leads5814 but does not include the third lead 5816.

Referring now to both FIGS. 28 and 29, the tip 5802 of the sensing probe5800 is in direct contact with the thermal well 5100, which includes azone 5402. The thermal well 5100 is hollow, and the inner part of zone5402 is formed such that it will be in mating contact with the sensingprobe tip 5802. As shown in this embodiment, the thermal well 5100 isdesigned to have a mating geometry with the sensing probe 5800. Thus,the geometry of the thermal well 5100 depends on the geometry of the tip5802 of the sensing probe 5800 and vice-versa.

6. Sensor Apparatus and Sensor Apparatus Systems

For purposes of description of the sensor apparatus, the sensorapparatus is described with respect to exemplary embodiments. Theexemplary embodiments are shown in FIGS. 26, 27, and FIG. 30, withalternate exemplary embodiments in FIGS. 28 and 29. In alternateembodiments of the sensor apparatus, the sensing probe can be usedoutside of the thermal well. However, the sensor apparatus has alreadybeen described herein alone. Thus, the description that followsdescribes one embodiment of the exemplary embodiment of the sensorapparatus which includes, for this purpose, a sensing probe and athermal well.

Alternate embodiments of thermal wells are described, often in relationto a fluid line. In most embodiments, the fluid line could be the fluidpath of a cassette, such as fluid path 2303 of exemplary cassette 2300,described above. Alternatively, the principles described below couldalso be applicable to any of the cassette embodiment described herein.

Referring now to FIG. 30, in an exemplary embodiment, the sensing probe6000 shown in FIG. 13A and the thermal well 5100 are shown coupled andoutside of a fluid line. As described above, the thermal well 5100 canbe in a fluid line, a protective sleeve, any disposable, machine,chamber, cassette or container. However, for purposes of thisdescription of the exemplary embodiment, the thermal well 5100 is takento be anywhere where it is used to determine thermal and/or conductiveproperties of a dialysate.

A dialysate is in contact with the outside of zone 5402 of the thermalwell 5100. Thermal energy is transferred from the dialysate to thethermal well 5100 and further transferred to the tip 6002 of the sensingprobe 6000. Thermal energy is then conducted to the thermal sensor 6014.The thermal sensor 6014 communicates via leads 6016 with equipment thatcan determine the temperature of the dialysate based on feedback of thethermal sensor 6014. In embodiments where conductivity sensing is alsodesired, lead 6018 communicates with equipment that can determine theconductivity of the dialysate. With respect to determining theconductivity of the dialysate, in addition to the lead 6018, a secondelectrical lead/contact (not shown) would also be used. The second leadcould be a second sensor apparatus as shown in FIG. 30, or,alternatively, a second probe that is not necessarily the same as thesensor apparatus shown in FIG. 30, but rather, any probe or apparatuscapable of sensing capacitance of the dialysate, including, anelectrical contact.

Heat transfer from the tip 6002 to the thermal sensor 6014 may beimproved by the use of a thermal epoxy or thermal grease 6022.

Referring now to FIGS. 28 and 29, in the alternate exemplary embodiment,whilst the sensing probe 5800 is coupled to the thermal well 5100, thetip 5802, having the geometry shown, forms an air gap 6402 between theinner zones 5404 and 5406 of the thermal well 5100 and the tip 5802. Theair gap 6402 provides an insulative barrier so that only the top of thesensing tip of 5802 is in communication with the top zone 5402 of thethermal well 5100.

The sensing probe 5800 and thermal well 5100 are shown coupled andoutside of a fluid line. As described above, the thermal well 5100 canbe in a fluid line, a protective sleeve, disposable unit, machine,non-disposable unit, chamber, cassette or container. However, forpurposes of this description of the exemplary embodiment, the thermalwell 5100 is taken to be anywhere where it is used to determine thermaland/or conductive properties (FIG. 28) of a dialysate.

A dialysate is in contact with the outside of zone 5402 of the thermalwell 5100. Thermal energy is transferred from the dialysate to thethermal well 5100 and further transferred to the tip 5802 of the sensingprobe 5800. Thermal energy is then conducted to the thermal sensor 5808.The thermal sensor 5808 communicates via leads 5814 with equipment thatcan determine the temperature of the dialysate based on feedback of thethermal sensor 5808. In embodiments where conductivity sensing is alsodesired, lead 5816 communicates with equipment that can determine theconductivity of the dialysate. With respect to determining theconductivity of the dialysate, in addition to the lead 5816, a secondelectrical lead (not shown) would also be used. The second lead could bea second sensor apparatus as shown in FIG. 28, or, alternatively, asecond probe that is not necessarily the same as the sensor apparatusshown in FIG. 28, but rather, any probe or apparatus capable of sensingcapacitance of the dialysate, including, an electrical contact.

Heat transfer from the tip 5802 to the thermal sensor 5808 can beimproved by the use of a thermal epoxy or thermal grease 5812.

Referring now to FIG. 31, an alternate embodiment showing a sensingprobe 6602 coupled to a thermal well 5100 is shown. For purposes of thisdescription, any embodiment of the sensing probe 6602 and any embodimentof the thermal well 5100 can be used. In this embodiment, to increasethe thermal coupling between the tip of the sensing probe 6602 and thethermal well 5100, thermal grease 6604 is present at the interface ofthe tip of the sensing probe 6602 and the inner zone 5402 of the thermalwell 5100. In one embodiment, the amount of thermal grease 6604 is avolume sufficient to only be present in zone 5402. However, in alternateembodiments, larger or smaller volumes of thermal grease can be used.

Referring now to FIG. 32, a sensor apparatus system is shown. In thesystem, the sensor apparatus is shown in a device containing a fluidline 5108. The sensor apparatus includes the sensing probe 6000 and thethermal well 5100. In this embodiment, the thermal well 5100 and fluidline 5108 is a disposable portion and the sensing probe 6000 is areusable portion. Also in the reusable portion is a spring 6700. Thespring 6700 and sensing probe 6000 are located in a housing 6708. Thehousing 6708 can be in any machine, container, device or otherwise. Thespring 6700 can be a conical, a coil spring, wave spring, or urethanespring.

In this embodiment, the thermal well 5100 and the sensing probe 6000 mayinclude alignment features 6702, 6704 that aid in the thermal well 5100and sensing probe 6000 being aligned. The correct orientation of thethermal well 5100 and the sensing probe 6000 may aid in the mating ofthe thermal well 5100 and the sensing probe 6000 to occur. Theconfiguration of the space 6706 provides the sensing probe 6000 withspace for lateral movement. This allows the sensing probe 6000 to, ifnecessary; move laterally in order to align with the thermal well 5100for mating.

The sensing probe 6000 is suspended by a spring 6700 supported by theflange 6020. The spring 6700 allow vertical movement of the sensingprobe 6000 when the thermal well 5100 mates with the sensing probe 6000.The spring 6700 aids in establishing full contact of the sensing probe6000 and the thermal well 5100.

The fluid line 5108 can be in any machine, container, device orotherwise. The fluid line 5108 contains a fluid path 5104. A dialysateflows through the fluid path 5104 and the thermal well 5100, located inthe fluid line 5108 such that the thermal well 5100 has ample contactwith the fluid path 5104 and can sense the temperature properties and,in some embodiments, the conductive properties of the dialysate. Thelocation of the thermal well 5100 in the fluid path 5104, as describedin more detail above, may be related to the desired accuracy, thedialysate and other considerations.

The spring 6700 and sensing probe 6000 assembly, together with the space6706 in the housing 6708 may aid in alignment for the mating of thesensing probe 6000 and the thermal well 5100. The mating provides thethermal contact so that the thermal well 5100 and the sensing probe 6000are thermally coupled.

A wire 6710 is shown. The wire contains the leads. In some embodiments,there are two leads. Some of these embodiments are temperature sensing.In other embodiments, the wire contains three or more leads. Some ofthese embodiments are for temperature and conductivity sensing.

Referring now to FIG. 33, an alternate embodiment of the system shown inFIG. 17 is shown. In this embodiment, the sensing probe 6000 issuspended by a coil spring 6800. A retaining plate 6802 captures thecoil spring 6800 to retain the spring 6800 and sensing probe 6000. Inone embodiment, the retaining plate 6802 is attached to the housing 6708using screws. However, in alternate embodiments, the retaining plate6802 is attached to the housing 6708 using any fastening methodincluding but not limited to: adhesive, flexible tabs, press fit, andultrasonic welding. Aligning features 6806 on the housing 6708 aid inalignment of the sensing probe 6000 to a thermal well (not shown).Lateral movement of the sensing probe 6000 is provided for by clearancein areas 6808 in the housing 6708. A wire 6710 is shown. The wirecontains the leads. In some embodiments, there are two leads. Some ofthese embodiments are temperature sensing. In other embodiments, thewire contains three or more leads. Some of these embodiments are fortemperature and conductivity sensing.

Referring now to FIG. 34, a sensing probe 6000 is shown in a housing6708. In these embodiments, an alternate embodiment of a spring, aflexible member 6900, is integrated with the sensing probe 6000 to allowvertical movement of the sensing probe 6000 within the housing 6708. Aretaining plate 6902 captures the flexible member 6900 to retain theflexible member 6900 and sensing probe 6000. In one embodiment, theretaining plate 6902 is attached to the housing 6708 using screws.However, in alternate embodiments, the retaining plate 6902 is attachedto the housing 6708 using any fastening method including but not limitedto: adhesive, flexible tabs, press fit, and ultrasonic welding. Lateralmovement of the sensing probe 6000 is provided for by clearance in areas6908 in the housing 6708. A wire 6710 is shown. The wire contains theleads. In some embodiments, there are two leads. Some of theseembodiments are temperature sensing. In other embodiments, the wirecontains three or more leads. Some of these embodiments are fortemperature and conductivity sensing.

Referring now to FIG. 35, an alternate embodiment of a sensing probe6000 in a housing 7002 is shown. In this embodiment, flexible member7000 is attached or part of the housing 7002, provides for verticalmovement of the sensing probe 6000. In this embodiment, the openings7004, 7006 in housing 7002 are sized such that the sensing probe 6000experiences limited lateral movement. Flexible member 7000 acts on theflange 7008 on the sensing probe 6000. A wire 6710 is shown. The wirecontains the leads. In some embodiments, there are two leads. Some ofthese embodiments are temperature sensing. In other embodiments, thewire contains three or more leads. Some of these embodiments are fortemperature and conductivity sensing.

The flange, as shown and described with respect to FIG. 35, can belocated in any area desired on the sensing probe 6000. In otherembodiments, the sensing probe may be aligned and positioned by otherhousing configurations. Thus, the embodiments of the housing shownherein are only some embodiments of housings in which the sensorapparatus can be used. The sensor apparatus generally depends on beinglocated amply with respect to the dialysate. The configurations thataccomplish this can vary depending on the dialysate and the intended useof the sensing apparatus. Further, in some embodiments where the thermalwell is not used, but rather, the sensing probe is used only. Thehousing configurations may vary as well.

The sensing apparatus, in some embodiments, is used to senseconductivity. In some embodiments, this is in addition to temperaturesensing. In those embodiments where both temperature and conductivitysensing is desired, the sensing probe typically includes at least threeleads, where two of these leads may be used for temperature sensing andthe third used for conductivity sensing.

Referring now to FIG. 15, for conductivity sensing, at least two sensors7102, 7104 are located in an area containing the dialysate. In theembodiment shown, the area containing the dialysate is a fluid path 5104inside a fluid line 5108. The conductivity sensors 7102, 7104 can be oneof the various embodiments of sensing probes as described above, or oneof the embodiments of the sensor apparatus embodiments (including thethermal well) as described above. However, in other embodiments, onlyone of the sensors is one of the embodiments of the sensor apparatus orone of the embodiments of the sensing probe, and the second sensor isany electrical sensor known in the art. Thus, in the systems describedherein, conductivity and temperature can be sensed through using eitherone of the sensor apparatus or one of the sensor probes as describedherein and a second capacitance sensor, or one of the sensor apparatusor one of the sensor probes as described herein and an electricalsensor.

Referring now to FIG. 36, an alternate embodiment of a sensor apparatusincluding a sensing probe 7200 and a thermal well 5100 is shown in afluid line 5108. In this embodiment, the sensing probe 7200 isconstructed of a metal housing. The thermal well 5100 is alsoconstructed of metal. The thermal well 5100 and the sensing probe 7200can be made from the same metal or a different metal. The metal, in thepreferred embodiment, is a conductive metal, which may include stainlesssteel, steel, copper and silver. A lead 7202 is attached to the sensingprobe 7200 housing for conductivity sensing. The thermal sensing leads7204 are attached to a thermal sensor located inside the sensing probe7200 housing. In this embodiment, therefore, the third lead 7202 (or thelead for conductivity sensing) can be attached anywhere on the sensingprobe 7200 because the sensing probe 7200 is constructed of metal. Inthe previously described embodiments, where the sensing probe housingwas constructed of plastic, and the sensing tip constructed of metal,the third lead for conductivity sensing was attached to the sensing tip.

A known volume of dialysate may be used to determine conductivity. Thus,two sensors may be used and the volume of fluid between the two sensorscan be determined. Conductivity sensing is done with the two electricalcontacts (as described above), where one or both can be the sensorapparatus. The volume of dialysate between the two contacts is known.

Conductivity sensing is done by determining the conductivity from eachof the sensors and then determining the difference. If the difference isabove a predetermined threshold, indicating an abnormal difference inconductivity between the first and second sensor (the designations“first” and “second” being arbitrary), then it can be inferred that airmay be trapped in the dialysate and a bubble detection alarm may begenerated to indicate a bubble. Thus, if there is a large decrease inconductivity (and likewise, a large increase in resistance) between thefirst and second sensor, air could be trapped and bubble presence may bedetected.

Leaks in a machine, system, device or container may be determined usingthe conductivity sensing. Where a sensing apparatus is in a machine,device or system, and that sensing apparatus senses conductivity, in oneembodiment, a lead from the sensor apparatus (or electrical contacts) toan analyzer or computer machine may be present.

In some embodiments, the analyzer that analyzes the electrical signalsbetween the contacts is connected to the metal of the machine, device,system or container. If the analyzer senses an electrical signal fromthe machine, then a fluid leak may be inferred.

The cassette embodiments shown and described in this description includeexemplary and some alternate embodiments. However, any variety ofcassettes are contemplated that include similar or additionalfunctionality. As well, the cassettes may have varying fluid pathsand/or valve placement and may utilize pumping functions, valvingfunctions, and/or other cassette functions. All of these embodiments arewithin the scope of the invention.

While the principles of the invention have been described herein, it isto be understood by those skilled in the art that this description ismade only by way of example and not as a limitation as to the scope ofthe invention. Other embodiments are contemplated within the scope ofthe present invention in addition to the exemplary embodiments shown anddescribed herein. Modifications and substitutions by one of ordinaryskill in the art are considered to be within the scope of the presentinvention.

1. A method for determining temperature and conductivity of a dialysatein a peritoneal dialysis pump cassette, said pump cassette comprising afirst region formed of a flexible membrane and a second region formed ofa rigid material and not comprising a flexible membrane, said secondregion having at least two thermal wells formed in the rigid materialand extending into a liquid flow path in the cassette, at least one ofsaid thermal wells having at least a portion comprising an electricallyconductive material configured for contacting a liquid contained in saidliquid flow path, said method comprising the steps of: placing thecassette in a dialysis machine having at least two sensing probes, eachsensing probe adapted to mate with one of the thermal wells; thermallycoupling each thermal well with a sensing probe such that temperatureand conductivity can be determined; transferring thermal andconductivity signals through at least 3 leads from at least one of saidsensing probes; and determining temperature and conductivity of a liquidcontained in the liquid flow path using said signals.
 2. The method ofclaim 1, wherein the pump cassette comprises a first side comprising thefirst region formed of the flexible membrane, a second side opposite thefirst side, and a third side comprising the second region having the atleast two thermal wells.
 3. A method for determining the temperature andconductivity of dialysate in a peritoneal dialysis pump cassette, saidpump cassette comprising a first region formed of a flexible membraneand a second region formed of a rigid material and not comprising aflexible membrane, said second region having at least two thermal wellsformed in the rigid material and extending into a liquid flow path inthe cassette, at least one of said thermal wells having at least aportion comprising an electrically conductive material configured forcontacting a liquid contained in said liquid flow path, said methodcomprising the steps of: placing the cassette in a dialysis machinehaving at least two sensing probes, each sensing probe adapted to matewith one of the thermal wells; thermally coupling each thermal well witha sensing probe such that temperature and conductivity can bedetermined; transferring thermal and conductivity signals through atleast 3 leads from at least one of said sensing probes; determiningtemperature and conductivity of a liquid contained in the liquid flowpath using said signals; and comparing the conductivity determined to apreset conductivity level.
 4. A method according to claim 3, whereinsaid method further comprises the step of sending a signal to thedialysis machine if the determined conductivity is not within aspecified range of the preset conductivity level.
 5. A method accordingto claim 4, wherein said method further comprises the step of suspendingperitoneal dialysis treatment if the determined conductivity is notwithin the specified range of the preset conductivity level.
 6. Themethod of claim 3, wherein the pump cassette comprises a first sidecomprising the first region formed of the flexible membrane, a secondside opposite the first side, and a third side comprising the secondregion having the at least two thermal wells.
 7. A disposable pumpcassette for performing peritoneal dialysis comprising: a) a first sidecomprising a flexible membrane for pumping or directing liquid in thecassette; b) an opposing second side adapted and configured to receive aforce urging at least a portion of the cassette against the flexiblemembrane when the cassette is mounted in a dialysis machine; and c) athird side not comprising a flexible membrane, wherein at least aportion of said third side: is not parallel to said first side; is notparallel to said opposing second side; spans at least a portion of thedistance separating said first side from said opposing second side; andcomprises a thermal well extending into a liquid path in the cassette,wherein the thermal well has a liquid side for making contact withliquid in the cassette and an opposing probe side for reversible matingwith a sensing probe, said thermal well being thermally conductivebetween the liquid side and the probe side.
 8. A cassette according toclaim 7, wherein the cassette comprises at least one pump chamber.
 9. Acassette according to claim 7, wherein the cassette comprises at leastone valving station.
 10. A cassette according to claim 7, wherein thecassette comprises at least one pump chamber and one valving station.11. A cassette according to claim 7, wherein the thermal well is a firstthermal well, and the cassette comprises a second thermal well spacedapart from the first thermal well, wherein the liquid side of the firstthermal well is in fluid communication with the liquid side of thesecond thermal well through a liquid flow path in the cassette.
 12. Acassette according to claim 11, wherein the first thermal well can bereversibly coupled with a first sensing probe, the second thermal wellcan be reversibly coupled with a second sensing probe, and at least aportion of each thermal well is electrically conductive, said couplingspermitting conductivity sensing of a liquid in the liquid flow path inthe cassette.
 13. A cassette according to claim 12, wherein at least oneof the first sensing probe and the second sensing probe has three leadsfor transmitting thermal and electrical conductivity signals.
 14. Acassette according to claim 7, wherein the well is secured to thecassette using at least one of press fit connection, flexible tabs,adhesive, ultrasonic weld, and a retaining plate with fastener.
 15. Adisposable pump cassette for performing peritoneal dialysis comprising:a) a first region formed of a flexible membrane; and b) a second region,not co-planar with said first region, that is formed of a rigidmaterial, does not comprise a flexible membrane and has at least twothermal wells formed in the rigid material and extending into a liquidflow path in the cassette; wherein each thermal well has a liquid sidefor making contact with liquid in the cassette and an opposing probeside for reversible mating with a sensing probe, each thermal well beingthermally conductive between the liquid side and the probe side.
 16. Acassette according to claim 15, wherein the cassette comprises at leastone pump chamber.
 17. A cassette according to claim 15, wherein thecassette comprises at least one valving station.
 18. A cassetteaccording to claim 15, wherein the cassette comprises at least one pumpchamber and one valving station.
 19. A cassette according to claim 15,wherein the thermal wells are spaced apart from each other and whereinthe liquid side of each thermal well is in fluid communication with theliquid side of each other thermal well through the liquid flow path inthe cassette.
 20. A cassette according to claim 19, wherein a firstthermal well can be reversibly coupled with a first sensing probe, asecond thermal well can be reversibly coupled with a second sensingprobe, and at least a portion of each thermal well is electricallyconductive, said couplings permitting conductivity sensing of a liquidin the liquid flow path.
 21. A cassette according to claim 20, whereinat least one of the first sensing probe and the second sensing probe hasthree leads for transmitting thermal and electrical conductivitysignals.
 22. A cassette according to claim 15, wherein the at least twowells are secured to the cassette using at least one of press fitconnection, flexible tabs, adhesive, ultrasonic weld, and a retainingplate with fastener.